<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>CamShift Example</title>
<link href="js_example_style.css" rel="stylesheet" type="text/css" />
</head>
<body>
<h2>CamShift Example</h2>
<p>
    Click <b>Start/Stop</b> button to start or stop the video.<br>
    The <b>videoInput</b> is a &lt;video&gt; element used as CamShift input.
    The <b>canvasOutput</b> is a &lt;canvas&gt; element used as CamShift output.<br>
    The code of &lt;textarea&gt; will be executed when video is started.
    You can modify the code to investigate more.
</p>
<div>
<div class="control"><button id="startAndStop" disabled>Start</button></div>
<textarea class="code" rows="29" cols="100" id="codeEditor" spellcheck="false">
</textarea>
</div>
<p class="err" id="errorMessage"></p>
<div>
    <table cellpadding="0" cellspacing="0" width="0" border="0">
    <tr>
        <td>
            <video id="videoInput" width="320" height="240" muted loop></video>
        </td>
        <td>
            <canvas id="canvasOutput" width="320" height="240"></canvas>
        </td>
        <td></td>
        <td></td>
    </tr>
    <tr>
        <td>
            <div class="caption">videoInput</div>
        </td>
        <td>
            <div class="caption">canvasOutput</div>
        </td>
        <td></td>
        <td></td>
    </tr>
    </table>
</div>
<script src="https://webrtc.github.io/adapter/adapter-5.0.4.js" type="text/javascript"></script>
<script src="utils.js" type="text/javascript"></script>
<script id="codeSnippet" type="text/code-snippet">
let video = document.getElementById('videoInput');
let cap = new cv.VideoCapture(video);

// take first frame of the video
let frame = new cv.Mat(video.height, video.width, cv.CV_8UC4);
cap.read(frame);

// hardcode the initial location of window
let trackWindow = new cv.Rect(150, 60, 63, 125);

// set up the ROI for tracking
let roi = frame.roi(trackWindow);
let hsvRoi = new cv.Mat();
cv.cvtColor(roi, hsvRoi, cv.COLOR_RGBA2RGB);
cv.cvtColor(hsvRoi, hsvRoi, cv.COLOR_RGB2HSV);
let mask = new cv.Mat();
let lowScalar = new cv.Scalar(30, 30, 0);
let highScalar = new cv.Scalar(180, 180, 180);
let low = new cv.Mat(hsvRoi.rows, hsvRoi.cols, hsvRoi.type(), lowScalar);
let high = new cv.Mat(hsvRoi.rows, hsvRoi.cols, hsvRoi.type(), highScalar);
cv.inRange(hsvRoi, low, high, mask);
let roiHist = new cv.Mat();
let hsvRoiVec = new cv.MatVector();
hsvRoiVec.push_back(hsvRoi);
cv.calcHist(hsvRoiVec, [0], mask, roiHist, [180], [0, 180]);
cv.normalize(roiHist, roiHist, 0, 255, cv.NORM_MINMAX);

// delete useless mats.
roi.delete(); hsvRoi.delete(); mask.delete(); low.delete(); high.delete(); hsvRoiVec.delete();

// Setup the termination criteria, either 10 iteration or move by atleast 1 pt
let termCrit = new cv.TermCriteria(cv.TERM_CRITERIA_EPS | cv.TERM_CRITERIA_COUNT, 10, 1);

let hsv = new cv.Mat(video.height, video.width, cv.CV_8UC3);
let hsvVec = new cv.MatVector();
hsvVec.push_back(hsv);
let dst = new cv.Mat();
let trackBox = null;

const FPS = 30;
function processVideo() {
    try {
        if (!streaming) {
            // clean and stop.
            frame.delete(); dst.delete(); hsvVec.delete(); roiHist.delete(); hsv.delete();
            return;
        }
        let begin = Date.now();

        // start processing.
        cap.read(frame);
        cv.cvtColor(frame, hsv, cv.COLOR_RGBA2RGB);
        cv.cvtColor(hsv, hsv, cv.COLOR_RGB2HSV);
        cv.calcBackProject(hsvVec, [0], roiHist, dst, [0, 180], 1);

        // apply camshift to get the new location
        [trackBox, trackWindow] = cv.CamShift(dst, trackWindow, termCrit);

        // Draw it on image
        let pts = cv.rotatedRectPoints(trackBox);
        cv.line(frame, pts[0], pts[1], [255, 0, 0, 255], 3);
        cv.line(frame, pts[1], pts[2], [255, 0, 0, 255], 3);
        cv.line(frame, pts[2], pts[3], [255, 0, 0, 255], 3);
        cv.line(frame, pts[3], pts[0], [255, 0, 0, 255], 3);
        cv.imshow('canvasOutput', frame);

        // schedule the next one.
        let delay = 1000/FPS - (Date.now() - begin);
        setTimeout(processVideo, delay);
    } catch (err) {
        utils.printError(err);
    }
};

// schedule the first one.
setTimeout(processVideo, 0);
</script>
<script type="text/javascript">
let utils = new Utils('errorMessage');

utils.loadCode('codeSnippet', 'codeEditor');

let streaming = false;
let videoInput = document.getElementById('videoInput');
let startAndStop = document.getElementById('startAndStop');
let canvasOutput = document.getElementById('canvasOutput');
let canvasContext = canvasOutput.getContext('2d');

startAndStop.addEventListener('click', () => {
    if (!streaming) {
        utils.clearError();
        videoInput.play().then(() => {
            onVideoStarted();
        });
    } else {
        videoInput.pause();
        videoInput.currentTime = 0;
        onVideoStopped();
    }
});

function onVideoStarted() {
    streaming = true;
    startAndStop.innerText = 'Stop';
    videoInput.height = videoInput.width * (videoInput.videoHeight / videoInput.videoWidth);
    utils.executeCode('codeEditor');
}

function onVideoStopped() {
    streaming = false;
    canvasContext.clearRect(0, 0, canvasOutput.width, canvasOutput.height);
    startAndStop.innerText = 'Start';
}

utils.loadOpenCv(() => {
    videoInput.addEventListener('canplay', () => {
        startAndStop.removeAttribute('disabled');
    });
    videoInput.src = 'cup.mp4';
});
</script>
</body>
</html>
